In order for a receiver to coherently demodulate data signal, a known signal called a pilot signal is used. In the case of Orthogonal Frequency Division Multiplexing (OFDM), the pilot signal has been added in time and frequency. A set of pilot signals (often called pilot tones) and time slots must be reserved in order to do frequency domain estimation of the channel transfer response. The number of pilot signals needs to be large enough to yield a reliable prediction of channel response at the tones used for transporting data. The pilot signal is an overhead in the system and therefore, only adequate allocation of pilot signals and time slots are needed to obtain a good channel estimation which facilitates data demodulation. For the uplink or reverse link access (i.e., mobile unit to base transmission), pilot signaling may occupy a large portion of sub-carriers when many users are simultaneously transmitting since each mobile unit needs to transmit its own pilot signal. This causes the overall wireless system throughput to be significantly reduced if there exists many low data rate users.
Accordingly, it would be highly desirable to have method and apparatus that addresses the deficiencies found in the prior art.
Elements in the Figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the Figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Furthermore, the terms “first”, “second”, and the like herein, if any, are used inter alia for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. Moreover, the terms “front”, “back”, “top”, “bottom”, “over”, “under”, and the like in the Description and/or in the Claims, if any, are generally employed for descriptive purposes and not necessarily for comprehensively describing exclusive relative position. Any of the preceding terms so used may be interchanged under appropriate circumstances such that various embodiments of the invention described herein may be capable of operation in other configurations and/or orientations than those explicitly illustrated or otherwise described.